The Washington Post reports more than 187,000 students have been exposed to gun violence at school in the 19 years since the Columbine High School massacre in 1999. Despite the high number, school shootings represent only a tiny fraction of U.S. gun violence, which claims more than 13,000 lives each year.

The Post’s report comes days ahead of Saturday’s historic March for Our Lives rally in Washington, D.C., which will be led by student survivors of the Parkland, Florida, high school massacre.